Bacterial sporulation represents an ideal system for studying the selective control of one expression during a simple cellular differentiation process. The molecular mechanisms regulating Bacillus subtilis sporulation will be defined by genetic, physiological and biochemical techniques. We will study sporulation-specific mutations affecting RNA polymerase DNA polymerases I and III, ribosomal proteins, and a serine protease. The physiological and biochemical characterization of these mutants will provide detailed information concerning the transcriptional, translational, post-translational and DNA replication mechanisms responsible for normal and abnormal cellular development.